Laminated packaging material comprising a barrier film and packaging containers manufactured therefrom

ABSTRACT

A packaging laminate that includes a barrier film having a PECVD barrier coating of diamond-like carbon is disclosed, along with a method of manufacturing such films, and laminated packaging materials comprising such films, in particular intended for liquid food packaging are disclosed. Packaging containers that include the laminated packaging material or being made from the laminated packaging material, in particular to a packaging container intended for liquid food packaging are also disclosed.

TECHNICAL FIELD

The present invention relates to a, laminated packaging materialcomprising a barrier film having a vapour deposited barrier coating ofamorphous diamond-like carbon, in particular intended for liquid foodpackaging, and to a method for manufacturing the laminated packagingmaterial.

Furthermore, the invention relates to packaging containers comprisingthe laminated packaging material or being made of the laminatedpackaging material in its entirety. In particular, the invention relatesto packaging containers intended for liquid food packaging, comprisingthe laminated packaging material.

BACKGROUND OF THE INVENTION

Packaging containers of the single use disposable type for liquid foodsare often produced from a packaging laminate based on paperboard orcarton. One such commonly occurring packaging container is marketedunder the trademark Tetra Brik Aseptic® and is principally employed foraseptic packaging of liquid foods such as milk, fruit juices etc, soldfor long term ambient storage. The packaging material in this knownpackaging container is typically a laminate comprising a bulk or corelayer of paper or paperboard and outer, liquid-tight layers ofthermoplastics. In order to render the packaging container gas-tight, inparticular oxygen gas-tight, for example for the purpose of asepticpackaging and packaging of milk or fruit juice, the laminate in thesepackaging containers normally comprises at least one additional layer,most commonly an aluminium foil.

On the inside of the laminate, i.e. the side intended to face the filledfood contents of a container produced from the laminate, there is aninnermost layer, applied onto the aluminium foil, which innermost,inside layer may be composed of one or several part layers, comprisingheat sealable thermoplastic polymers, such as adhesive polymers and/orpolyolefins. Also on the outside of the bulk layer, there is anoutermost heat sealable polymer layer.

The packaging containers are generally produced by means of modern,high-speed packaging machines of the type that form, fill and sealpackages from a web or from prefabricated blanks of packaging material.Packaging containers may thus be produced by reforming a web of thelaminated packaging material into a tube by both of the longitudinaledges of the web being united to each other in an overlap joint bywelding together the inner- and outermost heat sealable thermoplasticpolymer layers. The tube is filled with the intended liquid food productand is thereafter divided into individual packages by repeatedtransversal seals of the tube at a predetermined distance from eachother below the level of the contents in the tube. The packages areseparated from the tube by incisions along the transversal seals and aregiven the desired geometric configuration, normally parallelepipedic orcuboid, by fold formation along prepared crease lines in the packagingmaterial.

The main advantage of this continuous tube-forming, filling and sealingpackaging method concept is that the web may be sterilised continuouslyjust before tube-forming, thus providing for the possibility of anaseptic packaging method, i.e. a method wherein the liquid content to befilled as well as the packaging material itself are reduced frombacteria and the filled packaging container is produced under cleanconditions such that the filled package may be stored for a long timeeven at ambient temperature, without the risk of growth ofmicro-organisms in the filled product. Another important advantage ofthe Tetra Brik®-type packaging method is, as stated above, thepossibility of continuous high-speed packaging, which has considerableimpact on cost efficiency.

Packaging containers for sensitive liquid food, for example milk orjuice, can also be produced from sheet-like blanks or prefabricatedblanks of the laminated packaging material of the invention. From atubular blank of the packaging laminate that is folded flat, packagesare produced by first of all building the blank up to form an opentubular container capsule, of which one open end is closed off by meansof folding and heat-sealing of integral end panels. The thus closedcontainer capsule is filled with the food product in question, e.g.juice, through its open end, which is thereafter closed off by means offurther folding and heat-sealing of corresponding integral end panels.An example of a packaging container produced from sheet-like and tubularblanks is the conventional so-called gable-top package. There are alsopackages of this type which have a moulded top and/or screw cap made ofplastic.

A layer of an aluminium foil in the packaging laminate provides gasbarrier properties quite superior to most polymeric gas barriermaterials. The conventional aluminium-foil based packaging laminate forliquid food aseptic packaging is still the most cost-efficient packagingmaterial, at its level of performance, available on the market today.

Any other material to compete with the foil-based materials must becost-efficient regarding raw materials, have comparable food preservingproperties and have a comparably low complexity in the converting into afinished packaging laminate.

Among the efforts of developing non-aluminium-foil materials for liquidfood carton packaging, there is a general incentive towards developingpre-manufactured films or sheets having multiple barrierfunctionalities, i.e. not only oxygen and gas barrier but also watervapour, chemical- or aroma-substance barrier properties, which may justreplace the aluminium-foil barrier material, of the conventionallaminated packaging material, and adapt it to the conventional Al-foilprocess for lamination and manufacturing.

This is difficult, however, because most alternative barrier filmsprovide insufficient barrier and for mechanical strength properties to alaminated packaging material, generate too high total packaging materialcosts, or fail due to both said aspects. In particular, films having twoor more consecutive layers for providing barrier properties, become tooexpensive to be economically feasible in a packaging laminate.

When it is necessary to complement the main barrier layer, or mainbarrier coating, of the film, with further layers in order to providesufficient barrier properties, or to provide improved mechanicalproperties to the barrier film, costs are added to the packagingmaterial structure as a whole, because such multi-barrier films andpackaging materials are much more expensive to manufacture.

DISCLOSURE OF THE INVENTION

It is, accordingly, an object of the present invention to overcome, orat least alleviate, the above-described problems in non-foil laminatedpackaging materials.

It is also a general object of the invention to provide a laminatedpackaging material having barrier properties as well as integrityproperties that fulfil the needs in liquid carton laminated packagingmaterials.

It is a further general object of the invention to provide packagingmaterials for oxygen-sensitive products, such as laminated packagingmaterials for liquid, semi-solid or wet food products, which do notcontain aluminium foil but have good gas and other barrier propertiesand are suitable for long-term, aseptic packaging at reasonable cost.

A particular object, is to provide a, relative to aluminium foil barriermaterials, cost-efficient, non-foil, paper- or paperboard-based,laminated packaging material, having good gas barrier properties, andgood integrity properties within the laminated material, for the purposeof manufacturing packages for long-term, aseptic food storage.

Yet a further object of the invention is to provide a cost-efficient,non-foil, paper- or paperboard-based and heat-sealable packaginglaminate having good gas barrier properties, and good internal adhesionbetween the layers, for the purpose of manufacturing aseptic packagingcontainers for long-term storage of liquid foods at maintainednutritional quality under ambient conditions.

These objects are thus attainable according to the present invention bythe laminated packaging material, the packaging container and the methodof manufacturing the packaging material, as defined in the appendedclaims.

With the term “long-term storage” in connection with the presentinvention, is meant that the packaging container should be able topreserve the qualities of the packed food product, i.e. nutritionalvalue, hygienic safety and taste, at ambient conditions for at least 1or 2 months, such as at least 3 months, preferably longer, such as 6months, such as 12 months, or more. With the term “package integrity”,is generally meant the package durability, i.e. the resistance toleakage or breakage of a packaging container. A main contribution tothis property is that within a packaging laminate there is provided goodinternal adhesion between adjacent layers of the laminated packagingmaterial. Another contribution comes from the material resistance todefects, such as pinholes, ruptures and the like within the materiallayers, and yet another contribution comes from the strength of thesealing joints, by which the material is sealed together at theformation of a packaging container. Regarding the laminated packagingmaterial itself, the integrity property is thus mainly focused on theadhesion of the respective laminate layers to its adjacent layers, aswell as the quality of the individual material layers.

According to a first aspect of the invention, the general objects areattained by a laminated packaging material for packaging of liquid foodproducts, comprising a barrier film, which barrier film comprises asubstrate layer in the form of a web or a sheet, a first barrier coatingof an amorphous diamond-like carbon (DLC) coating, coated to be incontiguous contact with the substrate layer, and a further, secondbarrier layer, which comprises a major proportion of polyamide, such as50 weight-% or higher, such as 60 weight-% or higher, such as 70weight-% or higher, and is coated to be in contiguous contact with thefree surface of the first DLC barrier coating, the laminated packagingmaterial further comprising a first outermost liquid tight, heatsealable polymer layer, applied on the barrier-coated side of thesubstrate layer, and a second innermost liquid tight, heat sealablepolymer layer on the opposite, inner and second side of the barrierfilm. The first outermost polymer layer provides the outermost surfaceof a packaging container made from the laminate packaging material, andthe second innermost polymer layer provides the innermost surface of apackaging container made from the packaging material to be in contactwith the packed product.

The barrier coating of an amorphous DLC is applied by vapour depositiononto the substrate layer and accordingly it is contiguous to the surfaceof the substrate layer. According to an embodiment, the substrate layeris a polymer film substrate. According to another embodiment, theoutermost and innermost liquid tight and heat sealable polymer layersare polyolefin layers.

The second barrier layer is preferably coated onto the first barriercoating by means of extrusion coating or extrusion lamination at anamount of from 4 to 6 g/m2.

A laminated packaging material according to an embodiment of theinvention is thus a laminated structure, as counted from the innermostlayer in the consecutive order, having an innermost heat-sealable andliquid-tight layer of a polyolefin, a substrate layer, a first DLCbarrier coating deposited onto the substrate layer, a polyamide orpolyamide blend barrier layer directly coated onto the first DLC barriercoating, and an outermost heat-sealable and liquid-tight layer of apolyolefin. One of the outermost liquid-tight and heat sealable polymerlayers is accordingly applied onto the further thermoplastic oxygenbarrier layer.

According to another embodiment, the laminated packaging materialfurther comprises a bulk layer of paper or paperboard or othercellulose-based material.

In a yet further embodiment, the packaging material further comprises abulk layer of paper or paperboard or other cellulose-based material, thefree surface of the second barrier layer being bonded to a first side ofthe bulk layer by at least one bonding layer, said first outermostliquid tight, heat sealable polymer layer is applied onto the opposite,second and outer, side of the bulk layer, while said second innermostliquid tight, heat sealable polymer layer is applied on the inner sideof the barrier film, i.e. the side of the barrier film which is oppositeto the side bonded to the bulk layer.

According to an embodiment of the laminated packaging material, the atleast one bonding layer binds together the second barrier layer of thebarrier film and the surface of said first side of the bulk layer.

The at least one bonding layer suitably comprises a thermoplasticpolymer, such as a polyolefin. According to a special embodiment thebonding layer is a polyolefin, such as in particular apolyethylene-based polyolefin copolymer or blend, including in themajority ethylene monomer units.

According to a further embodiment, the at least one bonding layercomprises a layer of low density polyethylene (LDPE), which is incontiguous contact with the bulk layer, and a layer of an adhesivepolyethylene, modified polyethylene, or a so-called polyethylene-basedtie layer, between the LDPE and the second barrier layer.

According to a yet further embodiment, the at least one bonding layercomprises a layer comprising a blend of low density polyethylene (LDPE)and an adhesive polymer, modified polymer or so-called compatibiliser,the bonding layer being in contiguous contact with the bulk layer, aswell as the the second barrier layer on the other side. According to afurther embodiment, the blend comprises from 70 to 90 weight-%, such asfrom 80 to 90 weight-%, such as about 85 weight-% of LDPE and from 10 to30, such as from 10-80 weight-% of ethylene acrylic acid copolymer(EAA). The blended layer is preferably applied at an amount from 12 to15 g/m2.

According to a further embodiment, the second barrier layer comprises athermoplastic polyamide polymer or a blend of more than 50 weight-% ofpolyamide with a further polymer, such as for example an ethylene vinylalcohol copolymer (EVOH). According to an embodiment, the bonding layeris binding the bulk layer to the barrier film by melt extrusionlaminating the bonding polymer layer between a web of the bulk layer anda web of the barrier film layer, and simultaneously pressing the threelayers together while being forwarded through a lamination roller nip,thus providing a laminated structure, i.e. by so-called extrusionlaminating the bulk layer to the barrier film. According to a specialembodiment, the bonding layer is co-extruded together with the secondbarrier layer, the two layers accordingly binding together a DLC-coatedsubstrate layer and the bulk layer, such that the second barrier layeris extrusion-coated to be in contiguous contact with the first DLCbarrier coating. In this embodiment, the DLC-coated substrate layer issurface treated just before the melt co-extrusion lamination operation,i.e. the surface of the DLC coated barrier film is treated by coronatreatment before the molten polymer of the second barrier layer isapplied onto it.

According to a further embodiment of the laminated packaging material,the substrate layer of the barrier film has an adhesion-promoting primercoating on its other side, opposite the side coated with the barriercoating, and the barrier film is bonded to the second innermost liquidtight, heat sealable polyolefin layer by means of the adhesion-promotingprimer coating. The purpose of the adhesion-promoting primer coating is,to create or improve the adhesion strength to an adjacentextrusion-coated polymer, such as a polyolefin-based polymer layer andthe contacting surface thereof.

In an embodiment of the laminated packaging material, theadhesion-promoting primer coating is a composition comprising a compoundselected from the group consisting of aminosilanes andpolyethyleneimines.

In a further embodiment of the laminated packaging material, theadhesion-promoting primer coating is a second coating of an amorphousdiamond-like coating (DLC).

In this case, the barrier film is constructed from the substrate layerbeing a polymer film, which polymer film has inherent barrier propertiesin the polymer material, such as in polyamide, polyethylene vinylalcohol(EVOH) polyester, PET or cyclo-olefin copolymers. The barrier film iscoated with a first and second DLC adhesion-promoting coating on eachside for the main purpose of providing good adhesion to adjacentthermoplastic polymers, such as polyolefins, such as preferablyethylene-based homo-, or co-polymers or blends. Low barrier propertiesmay be provided by the DLC-coatings also at low thicknesses, such that acombined barrier and adhesion effect is readily achieved from each ofthe DLC coatings. If further barrier properties are not needed, it ishowever also conceivable to merely employ the respective DLC barriercoatings for their excellent adhesive properties in extrusion laminationto melt-extruded polymer layers.

In another embodiment, the barrier film of the laminated packagingmaterial is a double polyamide-coated DLC barrier film, which comprisesa first barrier film being laminated and bonded to a further identicalor similar second barrier film by means of an interjacent thermoplasticbonding layer, such as a polyethylene layer, such as low densitypolyethylene (LDPE). The barrier coatings may be facing towards eachother with the interjacent thermoplastic bonding layer in between.Alternatively, the barrier coatings may be facing away from each other,such that the adhesion-promoting primer coatings are bonded to eachother by the interjacent thermoplastic bonding layer. A furtheralternative is to stack the two films to each other such that bothbarrier coatings are facing in the same direction. Such a doublepolyamide-coated DLC barrier film may be further laminated to a bulklayer.

In a further embodiment, a first barrier film is laminated and bonded toa further identical or similar second barrier film by means of aninterjacent thermoplastic bonding layer, the laminated packagingmaterial further comprising a first outermost liquid tight, heatsealable polymer layer on the opposite, not laminated side of the firstbarrier film and a second innermost liquid tight, heat sealable polymerlayer on the opposite, not laminated side of the second barrier film. Afurther laminated packaging material of the invention may be composed ofat least two, and up to several barrier films laminate to each other byinterjacent thermoplastic bonding layers in between. According to anembodiment of the laminated packaging material, the substrate layer is apolymer film selected from the group consisting of films based on any ofpolyethylene terephthalate (PET), mono- or biaxially oriented PET (OPET,BOPET), non- or mono- or biaxially oriented polyethylenefuranoate (PEF),oriented or non-oriented polybutylene terephthalate (PBT), polyethylenenapthanate (PEN), non-oriented polyamide, oriented polyamide (PA, OPA,BOPA), polyethylene vinyl alcohol (EVOH), polyolefins such aspolypropylene, mono- or biaxially oriented polypropylene (PP, OPP,BOPP), polyethylenes such as oriented or non-oriented high densitypolyethylene (HDPE), linear low density polyethylene (LLDPE) andcyclo-olefin co-polymers (COC), and blends of any of said polymers, or amultilayer film having a surface layer comprising any of said polymersor blends thereof.

According to a more specific embodiment of the laminated packagingmaterial, the polymer film substrate is a film selected from the groupconsisting of films based on polyesters or polyamides and blends of anyof said polymers, or a multilayer film having a surface layer comprisingany of said polymers or blends thereof.

According to another more specific embodiment of the laminated packagingmaterial, the polymer film substrate is a film selected from the groupconsisting of films based on any of polyethylene terephthalate (PET),mono- or biaxially oriented PET (OPET, BOPET), non- or mono- orbiaxially oriented polyethylenefuranoate (PEF), polybutyleneterephthalate (PBT), polyethylene napthanate (PEN), non-orientedpolyamide, oriented polyamide (PA, OPA, BOPA), and blends of any of saidpolymers, or a multilayer film having a surface layer comprising any ofsaid polymers or blends thereof.

Suitable polyamides for the second barrier layer are aliphaticpolyamides such as polyamide-6, or semi-aromatic polyamides, such asnylon-MXD6 or Selar or PA-6I,&T polyamide grades, and blends of two ormore of said aliphatic and semi-aromatic polyamides. The polyamide maybe further blended with a second polymer, such as a second barrierpolymer, such as polyethylene vinyl alcohol (EVOH).

According to another embodiment of the laminated packaging material, thefirst amorphous diamond-like carbon barrier coating is applied at athickness from 2 to 50 nm, such as from 5 to 40 nm, such as from 10 to40 nm, such as from 20 to 40 nm.

According to another embodiment, the second amorphous diamond-likecarbon coating, acting as an adhesion-promoting primer coating, isapplied at a thickness from 2 to 50 nm, such as from 2 to 10 nm, such asfrom 2 to 5 nm.

According to a specific embodiment of the laminated packaging material,the polymer film substrate is a polyethylene film, such as a low lineardensity polyethylene (LLDPE) film. According to another specificembodiment, the polymer film substrate is an oriented PET film.

According to a further specific embodiment of the laminated packagingmaterial, the polymer film substrate has a thickness of 12 μm or lower,such as from 8 to 12 μm, such as from 10 to 12 μm.

Thinner polymer film substrates do exist commercially and would befeasible within the scope of the present invention, but it is presentlynot realistic to go below 8 μm, and films thinner than 4 μm would bedifficult from a web-handling point of view in industrial coating andlamination processes for packaging. On the other hand, films thickerthan 12-15 μm are of course feasible but less interesting for laminatedpackaging materials of the invention, since they add too much strengthand toughness for the functionality of opening devices and perforations.According to an embodiment, the polymer film substrate should be 12 μmor below, such as an oriented PET film of from 10 to 12 μm, such asabout 12 μm. At higher thickness of the film substrate, the tearing andcutting properties of the laminated packaging material are impairedbecause of the higher strength of the material.

The packaging material comprising the barrier film having a barriercoating of vapour deposited amorphous diamond-like carbon, shows goodproperties in many respects, such as having low oxygen transmission rate(OTR), low water vapour transmission rate (WVTR), good aroma and odourbarrier properties and has good mechanical properties in subsequenthandling operations such as lamination into a laminated packagingmaterial and the fold-forming and sealing operations of such a laminatedmaterial into packages.

In particular, it has been seen that the laminated packaging materialaccording to the invention has excellent integrity, by providingexcellent adhesion between the adjacent layers within the laminatedconstruction and by providing good quality of the barrier coating undersevere conditions such as at high relative humidity in the laminatedmaterial layers. Especially, for the packaging of liquids, and wet food,it is important that the inter-layer adhesion within the laminatedpackaging material is maintained also under wet packaging conditions.Among various types of vapour deposition barrier coatings, it has beenconfirmed that this DLC type of vapour deposited barrier coatings,applied by means of a plasma coating technology, such as by plasmaenhanced chemical vapour deposition, PECVD, has excellent laminateintegrity properties. Barrier coatings from other types of vapourdeposition chemistry, such as SiOx or AlOx coatings, do not, on theother hand, show good integrity properties in a laminated material ofthe same kind under wet and humid conditions. This extraordinaryadhesion compatibility of DLC coatings to organic polymers, such as inparticular polyolefins, also under wet conditions was truly surprising,and makes such barrier films particularly suitable for liquid cartonlaminate packaging.

According to a second aspect of the invention, a packaging container isprovided, comprising the laminated packaging material of the inventionand intended for packaging of liquid, semi-solid or wet food. Accordingto an embodiment, the packaging container is manufactured from thelaminated packaging material of the invention. According to a furtherembodiment, the packaging container is in its entirety made of thelaminated packaging material.

According to a still further embodiment, the packaging container may beformed from the laminated packaging material partly sealed, filled withliquid or semi-liquid food and subsequently sealed, by sealing of thepackaging material to itself, optionally in combination with a plasticopening or top part of the package.

Over time, various vapour deposition barrier coatings have beenconsidered in designing laminated packaging materials that fulfil thegas barrier criteria as well as the needs of various mechanical andother physical properties. Vapour deposited barrier layers may beapplied by means of physical vapour deposition (PVD) or chemical vapourdeposition (CVD) onto a substrate surface of a film material. Thesubstrate material itself may contribute with some properties as well,but should above all have appropriate surface properties, suitable forreceiving a vapour deposition coating, and working efficiently in avapour deposition process.

Thin vapour deposited layers are normally merely nanometer-thick, i.e.have a thickness in the order of magnitude of nanometers, for example offrom 1 to 500 nm (50 to 5000 Å), preferably from 1 to 200 nm, morepreferably from 1 to 100 nm and most preferably from 1 to 50 nm.

One common type of vapour deposition coating, often having some barrierproperties, in particular water vapour barrier properties, is so calledmetallisation layers, e.g. aluminium metal physical vapour deposition(PVD) coatings.

Such a vapour deposited layer, substantially consisting of aluminiummetal may have a thickness of from 5 to 50 nm, which corresponds to lessthan 1% of the aluminium metal material present in an aluminium foil ofconventional thickness for packaging, i.e. 6.3 μm. While vapourdeposition metal coatings require significantly less metal material,they only provide a low level of oxygen barrier properties, at most, andneed to be combined with a further gas barrier material in order toprovide a final laminated material with sufficient barrier properties.On the other hand, it may complement a further gas barrier layer, whichdoes not have water vapour barrier properties, but which is rathersensitive to moisture.

Other examples of vapour deposition coatings are aluminium oxide (AlOx)and silicon oxide (SiOx) coatings. Generally, such PVD-coatings are morebrittle and less suitable for incorporation into packaging materials bylamination. Metallised layers as an exception do have suitablemechanical properties for lamination material despite being made by PVD,however generally providing a lower barrier to oxygen gas.

Other coatings which have been studied for laminated packaging materialsmay be applied by means of a plasma enhanced chemical vapour depositionmethod (PECVD), wherein a vapour of a compound is deposited onto thesubstrate under more or less oxidising circumstances. Silicon oxidecoatings (SiOx) may, for example, also be applied by a PECVD process,and may then obtain very good barrier properties under certain coatingconditions and gas recipes. Unfortunately, SiOx coatings show badadhesion properties when laminated by melt extrusion lamination topolyolefins and other adjacent polymer layers, and the laminatedmaterial is exposed to wet or highly humid packaging conditions.Special, expensive adhesives or adhesive polymers are needed to reachand maintain sufficient adhesion in a packaging laminate of the typeintended for liquid carton packaging.

According to this invention, the vapour deposition coating is anamorphous hydrogenated carbon barrier layer applied by a plasma enhancedchemical vapour deposition process, PECVD, a so-called diamond-likecarbon (DLC). DLC defines a class of amorphous carbon material thatdisplays some of the typical properties of diamond. Preferably, ahydrocarbon gas, such as e.g. acetylene or methane, is used as processgas in the plasma for producing the coating. As pointed out above, ithas been seen that such DLC coatings, provide good and sufficientadhesion to adjacent polymer or adhesive layers in a laminated packagingmaterial under wet testing conditions. Particularly good adhesioncompatibility with adjacent laminated polymer layers, i.e. polymerlayers which are adherent to or coated onto the DLC barrier coating, hasbeen seen with polyolefins and in particular polyethylene andpolyethylene-based co-polymers.

A DLC barrier coating thus provides good barrier and integrityproperties to liquid-filled packaging containers made from a packaginglaminate comprising a barrier film having the barrier coating, bycontributing with good mechanical properties, good barrier properties tovarious substances migrating through such laminated materials in eitherinward or outward direction from a filled package, as well as byresulting in excellent adhesion to adjacent polymer layers in alaminate. Further improved barrier properties are obtainable when theDLC barrier coating is coated to be in contiguous contact with a layercomprising a major proportion of a polyamide, such as at least 50weight-%. Accordingly, a barrier film from any substrate layer, such asa polyethylene film having only low oxygen barrier properties in itself,having a DLC barrier coating can provide a packaging laminate and apackaging container with sufficient oxygen barrier properties as well aswater vapour barrier properties, for long term ambient storage, such asfor up to 2-6 months, such as for up to 12 months. In addition, the DLCbarrier coating provides good barrier properties to various aroma andflavour substances present in the packed food product, to low-molecularsubstances possibly appearing in the adjacent layers of materials, andto odours and other gases than oxygen. Moreover, the DLC barriercoating, exhibits good mechanical properties, as coated on a polymerfilm substrate, when laminated into a carton-based packaging laminate,withstanding lamination and subsequent fold-forming of the packaginglaminate and sealing it into filled packages. Polyester and polyamidefilms provide excellent substrate surfaces for the initiation and thegrowth of a DLC coating layer, during the vapour deposition coatingprocess. Favourable conditions in the coating process result in improvedcoating quality, and thus the coating layer may be made thinner andstill achieve the desired barrier properties as well as adhesion andcohesion properties.

The crack-onset strain (COS) for a biaxially oriented PET film, coatedwith a DLC barrier coating, may be higher than 2%, and this can normallyrelate to the oxygen barrier properties of the coating not starting todeteriorate until straining the film above 2%.

The DLC barrier coating may be deposited onto a substrate by means of aplasma-assisted coating technology, such as by a magnetron electrodeplasma, capacitively coupled to the power, similar to the type describedin U.S. Pat. No. 7,806,981 or by a radio-frequency plasma enhancedchemical vapour deposition, inductively coupled and using a carbonaceousprecursor similar to the type described in European patent EP0575299B1.

According to an embodiment, the polymer film substrate is a BOPET filmof a thickness of 12 μm or lower, such as from 8 to 12 μm. Orientedfilms usually exhibit an increased strength and toughness againsttearing or cutting through the film, and when included in laminatedpackaging materials such films can cause difficulties in opening of apackage. By selecting as thin as possible polymer film substrates, theopenability of a subsequently laminated packaging material will not beimpaired, in comparison to laminated packaging materials in which thebarrier materials are more brittle and the polymer materials areentirely made by melt extrusion coating and melt extrusion lamination.PET films are robust and cost efficient films with good mechanicalproperties, and this makes them particularly suitable substrates for DLCvapour deposition coating, due to some inherent high temperatureresistance and relative resistance to chemicals and moisture. Thesurface of a PET film also has high smoothness and good affinity tovapour deposited DLC coatings and vice versa.

According to a further embodiment, the polymer film substrate is a BOPETfilm that has an adhesion primer coating applied to the other side ofthe BOPET film, in order to provide better bonding to adjacent layers onboth sides of the barrier film, when laminating the film into alaminated packaging material.

According to yet another embodiment, the polymer film substrate is aBOPET film that has an additional DLC coating applied to the other sideof the BOPET film layer, in order to provide better bonding to adjacentlayers on both sides of the barrier film, when laminating the film intoa laminated packaging material.

DLC coatings further have the advantage of being easy recyclable,without leaving residues in the recycled content that contain elementsor materials that are not naturally existing in nature and oursurrounding environment.

Suitable thermoplastic polymers for the outermost and innermost heatsealable liquid-tight layers in the laminated packaging material of theinvention, are polyolefins such as polyethylene and polypropylene homo-or co-polymers, preferably polyethylenes and more preferablypolyethylenes selected from the group consisting of low densitypolyethylene (LDPE), linear LDPE (LLDPE), single-site catalystmetallocene polyethylenes (m-LLDPE) and blends or copolymers thereof.According to a preferred embodiment, the outermost heat sealable andliquid-tight layer is an LDPE, while the innermost heat sealable,liquid-tight layer is a blend composition of m-LLDPE and LDPE foroptimal lamination and heat sealing properties.

The same thermoplastic polyolefin-based materials, in particularpolyethylenes, as listed regarding the outermost and innermost layers,are also suitable in bonding layers interior of the laminated material,i.e. between a bulk or core layer, such as paper or paperboard, and thebarrier film.

According to an alternative embodiment, suitable for the bonding layersinterior of the laminated material, i.e. between an outer heat sealablelayer and the barrier- or primer-coated substrate layer, or for bondingthe barrier film to the bulk layer in a mono- or multilayer such bondinglaminate layer, are also so-called adhesive thermoplastic polymers, suchas modified polyolefins, which are mostly based on LDPE or LLDPEco-polymers or, graft co-polymers with functional-group containingmonomer units, such as carboxylic or glycidyl functional groups, e.g.(meth)acrylic acid monomers or maleic anhydride (MAH) monomers, (i.e.ethylene acrylic acid copolymer (EAA) or ethylene methacrylic acidcopolymer (EMAA)), ethylene-glycidyl(meth)acrylate copolymer (EG(M)A) orMAH-grafted polyethylene (MAH-g-PE). Another example of such modifiedpolymers or adhesive polymers are so called ionomers or ionomerpolymers. Preferably, the modified polyolefin is an ethylene acrylicacid copolymer (EAA) or an ethylene methacrylic acid copolymer (EMAA).

Corresponding modified polypropylene-based thermoplastic adhesives orbonding layers may also be useful, depending on the requirements of thefinished packaging containers.

Such adhesive polymer layers or tie layers are normally applied togetherwith the respective outer layer or further bulk-to-barrier bondinglayers in a co-extrusion coating operation.

However, normally, the use of the above described adhesive polymersshould not be necessary for bonding to the DLC barrier coating of theinvention. Sufficient and adequate adhesion to polyamide as well aspolyolefin layers as adjacent layers have been concluded, at a level ofat least 200 N/m, such as at least 300 N/m. Adhesion measurements areperformed at room temperature with a 180° degrees peel force testapparatus (Telemetric Instrument AB), 24 h after the LDPE lamination.Peeling is performed at the DLC/LDPE interface, the peel-arm being thebarrier film. When needed, distilled water droplets are added to thepeeled interface during peeling to assess the adhesion under wetconditions, i.e. the conditions when the laminated packaging materialhas been saturated with migrating moisture through the material layers,from the liquid stored in a packaging container made from the laminatedmaterial, and/or by storage in a wet or highly humid environment. Thegiven adhesion value is given in N/m and is an average of 6measurements.

A dry adhesion of more than 200 N/m ensures that the layers do notdelaminate under normal package manufacturing conditions, e.g. whenbending and fold-forming the laminated material. A wet adhesion of thissame level ensures that the layers of the packaging laminate do notdelaminate after filling and package formation, during transport,distribution and storage. The interior bonding polymer layer may becoated directly onto the polymer film substrate having a DLC barrierlayer coated thereon, by using common techniques and machines, e.g.those known for the lamination of an aluminum foil, in particular hotlamination (extrusion) of the polymer layer from a molten polymer ontothe DLC barrier coating. Also, using a pre-made polymer film and bindingit directly to the barrier-coated carrier film by locally melting it,e.g. by applying heat with a hot cylinder or heated roller, is possible.From the above it is apparent that a DLC-coated barrier film can behandled in a similar way to an aluminium foil barrier in the laminationand conversion methods into a laminated packaging material, i.e. bymeans of extrusion lamination and extrusion coating. The laminationequipment and methods do not require any modification, by for exampleadding specific adhesive polymers or binder/tie layers as may berequired in previously known plasma coated materials. In addition, thenew barrier film including the DLC barrier layer coated thereon can bemade as thin as an aluminium foil without adversely affecting thebarrier properties in the final food package.

It has been seen that when laminating the DLC barrier coating surfacefor a DLC-coated PET film to an adjacent layer of polyamide, thecontributing oxygen barrier properties from the barrier film areincreased to an up to 5 times improved value. This barrier improvementby merely laminating the DLC barrier coating of the invention into alaminate with a further barrier layer, cannot be explained by a simplelaminate theory, according to which

1/OTR=SUMi(1/OTRi)

but it does, thus, improve the total barrier beyond the individualcontribution of OTR by each laminate layer. It is believed that theexcellent adhesion between the DLC coating and the polyamide surfaceleads to a particularly well integrated interface between the twomaterials, and thereby to improved oxygen barrier properties.

According to a further corresponding embodiment, in which the barrierfilm is a DLC-coated LLDPE polyethylene film substrate, or polypropylenefilm substrate, the corresponding improvement by coating the DLC barriercoating with a further second barrier layer of polyamide, was about 10times improved.

In a preferred embodiment of the invention, the peel force strengthbetween the DLC barrier coating layer and the further, laminating,bonding polymer layers as measured by the 180° peel test method underdry and wet conditions (by putting water at the peeling interface) (asdescribed above) is higher than 200 N/m, such as higher than 300 N/m. Adry adhesion of more than 200 N/m ensures that the layers do notdelaminate under normal manufacturing conditions, e.g. when bending andfold-forming the laminated material. A wet adhesion of the same levelensures that the layers of the packaging laminate do not delaminateafter filling and package formation, during transport, distribution andstorage.

EXAMPLES AND DESCRIPTION OF PREFERRED EMBODIMENTS

In the following, preferred embodiments of the invention will bedescribed with reference to the drawings, of which:

FIG. 1a is showing a schematic, cross-sectional view of a laminatedpackaging material of a multilayer film type, according to an embodimentof the invention,

FIG. 1b shows a schematic, cross-sectional view of a further embodimentof a laminated packaging material of the multilayer film type,

FIG. 2 is showing a schematic, cross-sectional view of a laminatedpackaging material comprising a bulk layer, according to anotherembodiment of the invention,

FIG. 3 is showing a schematic, cross-sectional view of a furtherlaminated packaging material comprising a bulk layer, according to afurther embodiment of the invention,

FIG. 4 shows schematically a method, for laminating the barrier film ofthe invention into a laminated packaging material of the type of FIGS. 2and 3, for liquid food packaging, having a core or bulk layer ofpaperboard or carton,

FIGS. 5a, 5b, 5c and 5d are showing typical examples of packagingcontainers produced from the laminated packaging material according tothe invention, and

FIG. 6 is showing the principle of how such packaging containers aremanufactured from the packaging laminate in a continuous, roll-fed,form, fill and seal process.

EXAMPLES

Films from 12 μm thick biaxially oriented polyethyleneterephthalate(BOPET Hostaphan RNK12 and RNK12-2DEF by Mitsubishi) were depositioncoated with various coatings by plasma enhanced chemical vapourdeposition (PECVD) under vacuum conditions, in a roll-to-roll plasmareactor. A diamond-like amorphous hydrogenated carbon coating, DLC, wascoated on some film samples, in line with the invention, while otherPECVD barrier coatings were coated on other samples. The other PECVDbarrier coatings, subject of comparative examples, were SiOx, wherein xvaried between 1.5 and 2.2, SiOxCy coatings and SiOxCyNz coatings,respectively, wherein (y+z)/x is from 1 to 1.5. These othersilicon-containing barrier coatings were formed from organosilanepre-cursor gas compounds. The film samples according to the invention,were coated by depositing an amorphous, hydrogenated diamond-likecoating DLC from a plasma formed from pure acetylene gas.

The plasma employed was capacitively coupled to the power delivered at40 kHz frequency, and magnetically confined by unbalanced magnetronelectrodes placed at a distance from the circumferential surface of arotating drum, which functioned as a combined film-web transportingmeans and electrode. The polymer film substrate was cooled by coolingmeans within the drum web-transporting means.

The DLC coating was in a first example applied to a thickness of about15-30 nm, and in a second example to a thickness of only about 2-4 nm.

The SiOx coatings were coated to a thickness of about 10 nm.

The thus barrier-coated substrate film samples, were subsequentlyextrusion coated with a 15 g/m2 thick layer of low density polyethylene(LDPE), of a type corresponding to LDPE materials of the laminatebonding layer that is conventionally used in order to extrusion laminatepaperboard to aluminium foil in liquid carton packaging laminates.

The adhesion between the thus extrusion coated LDPE layer and thebarrier-coated substrate PET film, was measured by a 180° peel testmethod under dry and wet conditions (by putting distilled water at thepeeling interface) as described above. An adhesion of more than 200 N/mensures that the layers do not delaminate under normal manufacturingconditions, e.g. when bending and fold-forming the laminated material. Awet adhesion of this same level ensures that the layers of the packaginglaminate do not delaminate after filling and package formation, duringtransport, distribution and storage.

TABLE 1 PE- PE- laminate laminate Water Peel force Peel force OxygenVapour (N/m) (N/m) wet Coating type Barrier Barrier Dry adhesionadhesion SiOx (x = 1.5-2.2) <3 cc at 3 

N/A 40-50  0 Mean 1.5 cc SiOxCy (y/x = 1-1.5) <3 cc at 3 

1 40-50 40-50 Mean 1.5 cc SiOxCyNz <3 cc at 3 

1 200-300 100 (y + z/x = 1-1.5) Mean 1.5 cc DLC ~25 nm <3 cc at 3 

0.8 350-400 350-400 Mean 1.5 cc DLC ~25 nm on 0.5 ± 0.05 0.5 350-400350-400 both sides of film DLC 2-4 nm 60-80 5-6 350-400 350-400 DLC 2-4nm on 60-80 5-6 350-400 350-400 both sides of film

As can be seen from the results summarised in Table 1, there is someinsufficient dry adhesion between pure SiOx barrier coatings andthereonto extrusion coated LDPE, while the adhesion deterioratescompletely under wet/humid conditions.

When experimenting with more advanced SiOx formulas, containing alsocarbon and nitrogen atoms, some improvement is seen in the dry and/orwet adhesion properties, as compared to the pure SiOx coating, but thewet adhesion properties remain insufficient, i.e. below 200 N/m.

The dry adhesion of a DLC coating to extrusion coated LDPE is slightlybetter than for the best of the tested SiOxCyNz coatings. The moreimportant and unforeseeable difference, compared to the SiOxCyNzcoatings is that the adhesion remains constant under wet or humidconditions, such as are the conditions for laminated beverage cartonpackaging.

Furthermore, and rather surprisingly, the excellent adhesion of DLCcoatings at values above 200 N/m, remain unaffected also when the DLCcoating is made thinner, and as thin as 2 nm, i.e. where there isactually no notable barrier properties obtained any longer. This is thecase both regarding dry and wet conditions for the sample films.

Of course, when such films are laminated into packaging laminates ofpaperboard and thermoplastic polymer materials, it is advantageous tocoat such a DLC coating on both sides of the film, in order to provideexcellent adhesion on both sides of the film. Alternatively, theadhesion to adjacent layers on the opposite side of the substrate film,may be secured by a separately applied chemical primer composition, suchas the 2 DEF® primer from Mitsubishi. A DLC adhesion-promoting layer ispreferable from both environmental and cost perspective, since it onlyinvolves carbon atoms in the adhesion layer, and since it may be madevery thin in order to just provide adhesion, or thicker in order toprovide also barrier properties. At any thickness of a DLC-coating, theadhesion obtained is at least as good as that of a chemical primer (suchas the 2 DEF® from Mitsubishi) under both dry and wet conditions.

Thus, by the DLC-coated barrier films described above, high-integritypackaging laminates are provided, which have maintained excellentadhesion between layers also when used in liquid packaging, i.e. atsubjecting the packaging material to wet conditions, and which mayconsequently protect other layers of the laminate from deterioration, inorder to provide as good laminated material properties as possible.Since DLC coatings in general provide both good oxygen barrierproperties and water vapour barrier properties, it is a highly valuabletype of barrier coating to be used in carton package laminates forliquid food products.

In a second example, a DLC-coated, 30 g/m2 thick LLDPE blown film wasmeasured to have an OTR from 30 to 50 cc/m2/day/atm at 23° C. and 50%relative humidity RH. When coated with a second barrier layer of 4-6g/m2 of a blend of about 70 weight-% PA6 and about 30 weight-% PA-MXD6,the OTR was decreased down to 3-5 cc/m2/day/atm, i.e. the oxygen barrierwas times improved. The adhesion between the polyamide extrudate and theDLC barrier coating was very high, i.e. above 400 N/m.

In a third example, a similarly DLC-coated, 12 μm thick BOPET film wasmeasured to have an OTR from 1.5 to 2 cc/m2/day/atm at 23° C. and 50%relative humidity RH. When coated with a second barrier layer of 4-6g/m2 of a blend of about 70 weight-% PA6 and about 30 weight-% PA-MXD6,the OTR was decreased down to 0.4-0.9 cc/m2/day/atm i.e. the oxygenbarrier was 3-5 times improved. The adhesion between the polyamideextrudate and the DLC barrier coating was very high, i.e. above 400 N/m.

It is clear that the improvement level obtained by laminating the DLCbarrier coating to a further thermoplastic oxygen gas barrier layer, ishigh enough to compensate for a substrate layer having only low initialoxygen barrier properties, such as polyethylene of a lower density, suchas LLDPE. This phenomenon can thus be used in a laminated packagingmaterial structure according to the invention, further adding outermostheat sealable and liquid-tight layers to the laminated structure, and inthe preferred case also comprising a paperboard core layer, to providefor dimensionally stable packages, filled with or to be filled withliquid or semi-liquid or semi-solid food. Such packages were producedand the oxygen barrier properties were very favourable and deemedsuitable for liquid food packaging with higher requirements on shelflife and long-term storage.

Further, relating to the attached figures:

In FIG. 1a , there is shown, in cross-section, a first embodiment of alaminated packaging material, 10, of the invention. It comprises abarrier film 11 having a substrate layer 11 a of a polymer film having asurface of PET or PA, in this case an oriented PET (BOPET) film having athickness of 12 μm, wherein the substrate layer is coated with an,amorphous DLC coating 11 b, by means of a plasma enhanced chemicalvapour deposition, PECVD, coating, and a further, second barrier layer11 e from a blend of PA-6 and PA-MXD6 at a 70:30 blending ratio and atabout 5 g/m2, by means of extrusion coating, in order to even furtherimprove the oxygen barrier (decrease the OTR value) of the barrier film.The vapour deposited coating 11 b is a hydrogenated carbon coating (C:H)which is evenly deposited to a substantially transparent coating. Thethickness of the DLC coating is 20 to 40 μm. On its other side, oppositeto the DLC barrier coating, the film substrate is coated with a thinlayer of an adhesion-promoting primer 11 c, such as 2-DEF, a primingcomposition from Mitsubishi Chemicals. The barrier film is laminated toa layer of a thermoplastic and heat sealable polymer layer on each side,12,13, which may or may not be identical. The thermoplastic and heatsealable polymer layers are preferably polyolefin based polymers, andform the outermost, heat sealable layers of the laminate.

According to an alternative embodiment, the barrier film 11 asschematically shown in FIG. 1a , has instead, on its other side,opposite to the DLC barrier coating, been coated with a different thinlayer of an adhesion-promoting, and/or barrier coating, layer 11 c, of afurther DLC PECVD coating.

In FIG. 1b , a similar barrier film 11 is provided, by a polymer filmsubstrate 11 a as in FIG. 1a , i.e. a BOPET film substrate, being vapourdeposition coated on the coating side with a similar, amorphous DLCcoating 11 b, by means of plasma enhanced chemical vapour depositioncoating, PECVD, and further extrusion coated with a second barrier layer11 c from a blend of PA-6 and PA-MXD6 at a 70:30 blending ratio and atabout 5 g/m2, in order to even further improve the oxygen barrier(decrease the OTR value). On its other side, opposite to the DLC barriercoating, the film substrate may be coated with a thin layer of anadhesion-promoting primer 11 c of a DLC PECVD coating. The barrier film11 is laminated to a further identical or similar barrier film 11; 11 d,by means of interjacent bonding layer 16 of a thermoplastic polymer,such as a polyolefin or modified polyolefin layer, such as a layer ofLLDPE or a multilayer configuration of several individually identical ordifferent polyethylene layers. The intermediate bonding layers are thusbonding to the surfaces of the second barrier layers 11 e of bothbarrier films 11; 11 d, and are the bonding layer(s) 16 and the secondbarrier layers 11 e, which are co-extruded as melt co-extrusion layersand thus laminating the two films 11; 11 d together.

On each side the barrier film is laminated to a layer of a thermoplasticand heat sealable polymer layer 12,13. Thus, the outermost layers ofthermoplastic and heat sealable polymer are each contacting theadhesion-promoting primer coatings 11 c, of a DLC primer coating of eachof the barrier films 11; 11 d. A possible alternative adhesion-promotingcoating 11 c could be a chemical primer coating of the type 2 DEF® fromMitsubishi.

In a further embodiment not shown, the outermost layer of athermoplastic and heat sealable polymer layer 12; 22; 32, which is toconstitute the outside of a packaging container made of the laminatedmaterial, is applied onto a bulk layer 14; 21; 31, which is laminatedand positioned between the double barrier film obtained above and theoutermost layer 12, the double barrier film being the double structurein which the intermediate bonding layer is bonding together the DLCbarrier coating surfaces 11 b of two barrier films 11; 11 d. The doublebarrier film may contain further DLC coatings 11 c for barrier and/orfor adhesion-promotion purposes.

In FIG. 2, a laminated packaging material 20 of the invention, forliquid carton packaging, is shown, in which the laminated materialcomprises a paperboard bulk layer 21, having a bending force of 320 mN,and further comprises an outer liquid tight and heat sealable layer 22of polyolefin applied on the outside of the bulk layer 21, which side isto be directed towards the outside of a packaging container producedfrom the packaging laminate. The polyolefin of the outer layer 22 is aconventional low density polyethylene (LDPE) of a heat sealable quality,but may include further similar polymers, including LLDPEs. An innermostliquid tight and heat sealable layer 23 is arranged on the opposite sideof the bulk layer 21, which is to be directed towards the inside of apackaging container produced from the packaging laminate, i.e. the layer23 will be in direct contact with the packaged product. The thusinnermost heat sealable layer 23, which is to form the strong seals of aliquid packaging container made from the laminated packaging material,comprises one or more in combination of polyethylenes selected from thegroups consisting of LDPE, linear low density polyethylene (LLDPE), andLLDPE produced by polymerising an ethylene monomer with a C4-C8, morepreferably a C6-C8, alpha-olefin alkylene monomer in the presence of ametallocene catalyst, i.e. a so called metallocene—LLDPE (m-LLDPE).

The bulk layer 21 is laminated to a barrier film 28, comprising asubstrate layer 24 of a polymer film, in this case an oriented PET filmhaving a thickness of 12 μm, which is coated on a first side with alayer of a thin

PECVD vapour deposited layer of amorphous, DLC barrier material, 25, ata thickness of from 2-50 nm, such as from 5 to 40 nm, and further coronatreated and coated with a second thermoplastic barrier layer 29 from ablend of PA-6 and PA-MXD6 at a 70:30 blending ratio and at about 5 g/m2.On its second, opposite, side, the polymer film substrate is coated withan adhesion-promoting primer 27, in this case 2-DEF, a primingcomposition from Mitsubishi Chemicals. The first, DLC-coated, side ofthe thus barrier-coated film 24 is laminated to the bulk layer 21 by anintermediate layer 26 of bonding thermoplastic polymer or by afunctionalised polyolefin-based adhesive polymer, in this example by alow density polyethylene (LDPE) and by the further second thermoplasticbarrier layer 29, by coextrusion laminating the molten layers 26 and 29between the bulk layer and the DLC-coated film, while entering alamination roller nip. The intermediate bonding layer 26 is thus formedby means of extrusion laminating the bulk layer and the DLC-coated filmto each other, with the second thermoplastic barrier layer 29 beingadjacent and in direct contact with the DLC coating. The thickness ofthe intermediate bonding layer 26 is preferably from 7 to 20 μm, morepreferably from 12-18 μm. Excellent adhesion will be obtained betweenthese layers, providing good integrity of the laminated material, inthat the PECVD-coated DLC barrier coating is containing substantialamounts of carbon material, which exhibits good adhesion compatibilitywith organic polymers, such as polyolefins, such as in particularpolyethylene and polyethylene-based co-polymers. The innermost heatsealable layer 23 consists of two or several part-layers of the same ordifferent kinds of LDPE or LLDPE or blends thereof and has likewise goodadhesion and integrity with the adjacent primer-coated side of thebarrier film.

In FIG. 3, a laminated packaging material 30 of the invention, forliquid carton packaging, is shown, in which the laminated materialcomprises a paperboard bulk layer 31, having a bending force of 320 mN,and further comprises an outer liquid tight and heat sealable layer 32of polyolefin applied on the outside of the bulk layer 31, which side isto be directed towards the outside of a packaging container producedfrom the packaging laminate. The polyolefin of the outer layer 32 is aconventional low density polyethylene (LDPE) of a heat sealable quality,but may include further similar polymers, including LLDPEs. An innermostliquid tight and heat sealable layer 33 is arranged on the opposite sideof the bulk layer 31, which is to be directed towards the inside of apackaging container produced from the packaging laminate, i.e. the layer33 will be in direct contact with the packaged product. The thusinnermost heat sealable layer 33, which is to form the strongest sealsof a liquid packaging container made from the laminated packagingmaterial, comprises one or more in combination of polyethylenes selectedfrom the groups consisting of LDPE, linear low density polyethylene(LLDPE), and LLDPE produced by polymerising an ethylene monomer with aC4-C8, more preferably a C6-C8, alpha-olefin alkylene monomer in thepresence of a metallocene catalyst, i.e. a so called metallocene—LLDPE(m-LLDPE).

The bulk layer 31 is laminated to a barrier film 38, comprising asubstrate layer 34 of a polymer film, in this case an oriented PET filmhaving a thickness of 12 μm, which is coated on a first side with alayer of a thin PECVD vapour deposited layer of amorphous, DLC barriermaterial, 35 a, at a thickness of from 2-50 nm, such as from 5 to 40 nm,such as from 10 to nm, and further corona treated and coated with asecond thermoplastic barrier layer 35 c from a blend of PA-6 and PA-MXD6at a 70:30 blending ratio and at about 5 g/m2. On its second, opposite,side, the polymer film substrate is coated with a second amorphous DLCcoating 35 b. The second amorphous DLC coating may add barrierproperties too, but can also act merely as an adhesion promoting primercoating, and may then have a thickness as low as 2-4 nm. The first,DLC-coated, side of the thus barrier-coated film 34 is laminated to thebulk layer 31 by an intermediate layer 36 of bonding thermoplasticpolymer or by a functionalised polyolefin-based adhesive polymer, inthis example by a low density polyethylene (LDPE) and the further secondthermoplastic barrier layer 35 c, being coextrusion laminated betweenthe bulk layer and the DLC-coated film. The intermediate bonding layer36 and the second thermoplastic barrier layer 35 c are thus formed whilemelt co-extrusion laminating the bulk layer and the DLC-coated barrierfilm to each other. The thickness of the intermediate bonding layer 36is preferably from 7 to 20 μm, more preferably from 12-18 μm. Theinnermost heat sealable layer 33 may consist of two or severalpart-layers of the same or different kinds of LDPE or LLDPE or blendsthereof. Excellent adhesion will be obtained between these layers on theinside of the bulk layer 31, providing good integrity of the laminatedmaterial, in that the PECVD-coated DLC barrier coating is containingsubstantial amounts of carbon material, which exhibits good adhesioncompatibility with organic polymers, such as polyolefins, such as inparticular polyethylene and polyethylene-based co-polymers.

In FIG. 4, the lamination process 30 is shown, for the manufacturing ofthe packaging laminate 20; 30, of FIG. 2, and FIG. 3, respectively,wherein the bulk layer 41 is laminated to the barrier film 28; 38; 43 byextruding an intermediate bonding layer of LDPE 44 from an extrusionstation 45 and pressing together in a roller nip 46. The barrier film28; 38; 43 has an amorphous DLC barrier coating, deposited on thesurface of the polymer film substrate, whereby the DLC coating is to bedirected towards the bulk layer when laminated at the lamination station46. Subsequently, the laminated paper bulk and barrier film passes asecond extruder feedblock 47-2 and a lamination nip 47-1, where aninnermost heat sealable layer 23; 33; 47-3 is coated onto thebarrier-film side of the paper-film laminate forwarded from 46. Finally,the laminate, including an innermost heat sealable layer 47-3, passes athird extruder feedblock 48-2 and a lamination nip 48-1, where anoutermost heat sealable layer of LDPE 22; 32; 48-3 is coated onto theouter side of the paper layer. This latter step may also be performed asa first extrusion coating operation before lamination at 46, accordingto an alternative embodiment. The finished packaging laminate 49 isfinally wound onto a storage reel, not shown.

FIG. 5a shows an embodiment of a packaging container 50 a produced fromthe packaging laminate 20 according to the invention. The packagingcontainer is particularly suitable for beverages, sauces, soups or thelike. Typically, such a package has a volume of about 100 to 1000 ml. Itmay be of any configuration, but is preferably brick-shaped, havinglongitudinal and transversal seals 51 a and 52 a, respectively, andoptionally an opening device 53. In another embodiment, not shown, thepackaging container may be shaped as a wedge. In order to obtain such a“wedge-shape”, only the bottom part of the package is fold formed suchthat the transversal heat seal of the bottom is hidden under thetriangular corner flaps, which are folded and sealed against the bottomof the package. The top section transversal seal is left unfolded. Inthis way the half-folded packaging container is still is easy to handleand dimensionally stable when put on a shelf in the food store or on atable or the like.

FIG. 5b shows an alternative, preferred example of a packaging container50 b produced from an alternative packaging laminate 20 according to theinvention. The alternative packaging laminate is thinner by having athinner paper bulk layer 21, and thus it is not dimensionally stableenough to form a cuboid, parallellepipedic or wedge-shaped packagingcontainer, and is not fold formed after transversal sealing 52 b. Itwill thus remain a pillow-shaped pouch-like container and be distributedand sold in this form. Also packaging materials of the type described inconnection with FIG. 1b , are particularly suitable for such pouchpackages for liquid food and beverage.

FIG. 5c shows a gable top package 50 c, which is fold-formed from apre-cut sheet or blank, from the laminated packaging material comprisinga bulk layer of paperboard and the durable barrier film of theinvention. Also flat top packages may be formed from similar blanks ofmaterial.

FIG. 5d shows a bottle-like package 50 d, which is a combination of asleeve 54 formed from a pre-cut blanks of the laminated packagingmaterial of the invention, and a top 55, which is formed by injectionmoulding plastics in combination with an opening device such as a screwcork or the like. This type of packages are for example marketed underthe trade names of Tetra Top® and Tetra Evero®. Those particularpackages are formed by attaching the moulded top 55 with an openingdevice attached in a closed position, to a tubular sleeve 54 of thelaminated packaging material, sterilizing the thus formed bottle-topcapsule, filling it with the food product and finally fold-forming thebottom of the package and sealing it.

FIG. 6 shows the principle as described in the introduction of thepresent application, i.e. a web of packaging material is formed into atube 61 by the longitudinal edges 62 of the web being united to oneanother in an overlap joint 63. The tube is filled 64 with the intendedliquid food product and is divided into individual packages by repeatedtransversal seals 65 of the tube at a pre-determined distance from oneanother below the level of the filled contents in the tube. The packages66 are separated by incisions in the transversal seals and are given thedesired geometric configuration by fold formation along prepared creaselines in the material.

We have thus seen that the laminated packaging material of theinvention, enable the providing of packaging containers with goodintegrity properties also under wet conditions, i.e. for the packagingof liquid or wet food products with long shelf life.

The invention is not limited by the embodiments shown and describedabove, but may be varied within the scope of the claims.

1. A laminated packaging material for packaging of liquid food products,the laminated packaging material comprising: a barrier film, wherein thebarrier film comprises: a substrate layer in the form of a web or sheet,a first barrier coating of an amorphous diamond-like carbon (DCL) coatedto be in contiguous contact with the substrate layer, and a secondthermoplastic barrier layer, comprising a polyamide that is coated andin contiguous contact with the free surface of the first DLC barriercoating, wherein the laminated packaging material further comprises afirst outermost liquid tight, heat sealable polymer layer applied on thebarrier-coated side of the substrate layer, the first outermost polymerlayer is providing the outermost surface of a packaging container madefrom the laminate packaging material and a second, innermost liquidtight, heat sealable polymer layer on the opposite, inner and secondside of the barrier film, the second, innermost polymer layer isproviding the innermost surface of a packaging container made from thepackaging material to be in contact with the packed product.
 2. Thelaminated packaging material in claim 1, wherein the substrate layer isa polymer film substrate.
 3. The laminated packaging material in claim1, further comprising a bulk layer of paper or paperboard or othercellulose-based material.
 4. The laminated packaging material in claim1, further comprising a bulk layer of paper or paperboard or othercellulose-based material, and a second barrier layer, wherein the secondbarrier layer is laminated to a first side of the bulk layer by at leastone intermediate bonding layer, comprising a thermoplastic polymer, suchas a polyolefin, said first outermost liquid tight, heat sealablepolymer layer on the opposite, second and outer, side of the bulk layer,while said second innermost liquid tight, heat sealable polymer layer ison the inner side of the barrier film, which is opposite to the sidethat is bonded to the bulk layer.
 5. The laminated packaging material inclaim 4, wherein the at least one bonding layer comprises a layer of lowdensity polyethylene (LDPE), and wherein the LDPE is in contiguouscontact with the bulk layer, and a layer of an adhesive polyethylene,modified polyethylene, or a so-called polyethylene tie layer, betweenthe LDPE and the second barrier layer.
 6. The laminated packagingmaterial in claim 4, wherein the at least one bonding layer is a layercomprising a blend of low density polyethylene (LDPE) and an adhesive,modified polymer or so-called compatibiliser, and wherein the bondinglayer is in contiguous contact with the bulk layer, as well as thesecond barrier layer on the other side.
 7. The laminated packagingmaterial of claim 1, wherein the substrate layer of the barrier film hasan adhesion-promoting primer coating on its other side, opposite theside coated with the barrier coating, and wherein the barrier film isbonded to the second innermost liquid tight, heat sealable polyolefinlayer by the adhesion-promoting primer coating.
 8. The laminatedpackaging material of claim 7, wherein the adhesion-promoting primercoating is formed by a composition comprising one or more compoundsselected from the group consisting of aminosilanes andpolyethyleneimines.
 9. The laminated packaging material of claim 7,wherein the adhesion-promoting primer coating is a second coating of anamorphous diamond-like carbon (DLC).
 10. The laminated packagingmaterial of claim 1, wherein the barrier film of the laminated packagingmaterial is a double barrier film, which comprises a first barrier filmlaminated and bonded to a further identical or similar second barrierfilm by an interjacent thermoplastic bonding layer.
 11. The laminatedpackaging material of claim 1, wherein the substrate layer comprises apolymer film comprising a polymer selected from the group consisting ofa polyester a polyamide, an ethylene vinyl alcohol copolymer (EVOH), apolyolefin and a blend of any of said polymers, or wherein the substratelayer comprises a multilayer film having a surface layer comprising anyof said polymers or blends thereof.
 12. The laminated packaging materialof claim 1, wherein the second barrier layer comprises a polyamideselected from the group consisting of aliphatic polyamides,semi-aromatic polyamides, and blends of two or more of said aliphaticand semi-aromatic polyamides.
 13. The laminated packaging material ofclaim 1, wherein the second barrier layer further comprises an ethylenevinyl alcohol copolymer (EVOH).
 14. The laminated packaging material ofclaim 1, wherein the first, amorphous diamond-like carbon barriercoating is 2 to 50 nm thick.
 15. The laminated packaging material ofclaim 1, wherein the second amorphous diamond-like carbon coating,acting as an adhesion-promoting primer coating, is 2 to 50 nm thick. 16.The laminated packaging material of claim 1, wherein the substrate layeris a polyethylene film.
 17. The laminated packaging material of claim 1,wherein the substrate layer is an oriented PET film.
 18. The laminatedpackaging material of claim 1, wherein the substrate layer is 8 to 12 μmthick.
 19. The packaging container comprising the laminated packagingmaterial as defined in claim
 1. 20. The laminated packaging material ofclaim 1, wherein the second amorphous diamond-like carbon coating,acting as an adhesion-promoting primer coating, is 2 to 10 nm thick.